1. Field of the Invention
This invention relates to abrasive articles, and in particular to abrasive articles comprising a combination of grinding aids. In particular, this invention relates to abrasive articles comprising a combination of potassium tetrafluoroborate and a halogenated polymer in a binder, as well as abrasive articles comprising a combination of potassium tetrafluoroborate in a halogenated polymer binder.
2. Discussion of the Art
Abrasive articles generally comprise abrasive grains secured within a binder. In a bonded abrasive, the binder bonds the abrasive grains together in a shaped mass. Typically, this shaped mass is in the form of a wheel and thus it is commonly referred to as a grinding wheel. In nonwoven abrasives, the binder bonds the abrasive grains to a lofty, open, fibrous substrate. In coated abrasives, the binder bonds the abrasive grains to a substrate or backing. Coated abrasives may include a first coated layer bonded to one side of the backing (commonly referred to as a make coating), at least one layer of abrasive grains bonded to the backing by the make coating, and a second coating layer overlaying the abrasive particles. The second coating layer commonly is referred to as a size coating; it reinforces the retention of the abrasive particles. Coated abrasives also may include an additional "supersize" coating overlaying the size coating. The supersize coating may include a grinding aid.
Abrasive binders typically consist of a glutinous or resinous adhesive, and, optionally, additional ingredients. Examples of resinous adhesives include phenolic resins, epoxy resins, urethane resins, acrylate resins and urea formaldehyde resins. Examples of typical additives include grinding aids, fillers, wetting agents, surfactants, pigments, coupling agents, and dyes.
The addition of grinding aids can significantly affect the chemical and physical processes of abrading metals to bring about improved performance. It is believed that grinding aids either (1) decrease the friction between the abrasive grains and the workpiece being abraded, (2) prevent the abrasive grains from "capping", i.e., prevent metal particles from becoming welded to the tops of the abrasive grains, (3) decrease the interface temperature between the abrasive grains and the workpiece, and/or (4) decrease the required grinding force. Capping can occur when the grinding of metal by abrasive articles produces freshly formed, hot, and uncontaminated metal surfaces. If the newly formed, uncontaminated metal surface is not rapidly "contaminated", metal can transfer and adhere to the abrasive particles ("capping"), which decreases grinding performance. Grinding aids may prevent capping by rapidly contaminating the freshly formed metal surface.
U.S. Pat. No. 5,030,496 (McGurran) pertains to flexible and resilient, nonwoven, surface treating articles formed of entangled synthetic fibers bonded together at points where they contact one another by a binder resin comprising plasticized vinyl resin and polymerized melamine-formaldehyde derivative.
U.S. Pat. No. 5,378,251 (Culler et al.) teaches a structured abrasive article having abrasive composites comprising a binder, abrasive grains, and a grinding aid.
U.S. Pat. No. 4,253,850 (Rue) teaches reduced volume of abrasive and increased volume of filler to enhance performance in snagging wheels and wheel segments for conditioning billets, slabs, and castings. The majority of the claimed fillers are halogenated inorganic salts or polymers wherein at least 80% by volume of the filler material is inorganic material.
U.S. Pat. No. 5,221,295 (Zador) teaches a grinding aid formulation comprising a water insoluble, halogenated hydrocarbon grinding aid. The grinding aid contains at least 50% by weight halogen (chlorine or bromine). The grinding aid is stable up to about 400.degree. C., but decomposes below 600.degree. C. The formulation also comprises a polymeric binder which results in the formulation being cured to a coherent film. The preferred grinding aids are chlorinated waxes including paraffin waxes.
WO94/23898 (Helmin) pertains to a coated abrasive size or supersize coating comprising a cured grinding aid binder which is a blend of a thermoplastic resin and a thermoset resin and an effective amount of a grinding aid dispersed in the cured grinding aid binder. The thermoplastic can be either a water based (emulsion) or a solvent based thermoplastic. The addition of thermoplastic improves the rheology of the grinding aid binder prior to coating and improves the overall performance of the resulting coated abrasive.
The abrasive industry is always evaluating means to improve the abrading efficiency of abrasive articles without unduly increasing their cost. It is also desired to provide a means for utilizing a high concentration of grinding aid in an abrasive product without significantly reducing the strength of the binder.